pci: Add pci_device_route_intx_to_irq

Device assigned on KVM needs to know the mode
(enabled/inverted/disabled) and the IRQ number that a given device
triggers in the attached interrupt controller.

Add a PCI IRQ path discovery function that walks from a given device to
the host bridge, and gets this information.  For
this purpose, a host bridge callback function is introduced:
route_intx_to_irq. It is so far only implemented by the PIIX3, other
host bridges can be added later on as required.

Will be used for KVM PCI device assignment and VFIO.

Based on patch by Jan Kiszka, with minor tweaks.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/hw/piix_pci.c b/hw/piix_pci.c
index 09e84f59b6..8ece07c182 100644
--- a/hw/piix_pci.c
+++ b/hw/piix_pci.c
@@ -89,6 +89,7 @@ struct PCII440FXState {
 #define I440FX_SMRAM    0x72
 
 static void piix3_set_irq(void *opaque, int pirq, int level);
+static PCIINTxRoute piix3_route_intx_pin_to_irq(void *opaque, int pci_intx);
 static void piix3_write_config_xen(PCIDevice *dev,
                                uint32_t address, uint32_t val, int len);
 
@@ -315,6 +316,7 @@ static PCIBus *i440fx_common_init(const char *device_name,
                 pci_create_simple_multifunction(b, -1, true, "PIIX3"));
         pci_bus_irqs(b, piix3_set_irq, pci_slot_get_pirq, piix3,
                 PIIX_NUM_PIRQS);
+        pci_bus_set_route_irq_fn(b, piix3_route_intx_pin_to_irq);
     }
     piix3->pic = pic;
     *isa_bus = DO_UPCAST(ISABus, qbus,
@@ -386,6 +388,22 @@ static void piix3_set_irq(void *opaque, int pirq, int level)
     piix3_set_irq_level(piix3, pirq, level);
 }
 
+static PCIINTxRoute piix3_route_intx_pin_to_irq(void *opaque, int pin)
+{
+    PIIX3State *piix3 = opaque;
+    int irq = piix3->dev.config[PIIX_PIRQC + pin];
+    PCIINTxRoute route;
+
+    if (irq < PIIX_NUM_PIC_IRQS) {
+        route.mode = PCI_INTX_ENABLED;
+        route.irq = irq;
+    } else {
+        route.mode = PCI_INTX_DISABLED;
+        route.irq = -1;
+    }
+    return route;
+}
+
 /* irq routing is changed. so rebuild bitmap */
 static void piix3_update_irq_levels(PIIX3State *piix3)
 {